Over the last two decades a remarkable shift in focus has taken place in the nutrition field—we’ve gone from blaming fat for our expanding waistlines to fingering sugar instead. In the 1980s and 1990s the low-fat approach dominated dietary advice, with the premise that “fat makes you fat” and greasy cheeseburgers clog the arteries attaining the status of obvious truth. But with the surgeon general’s call to action about the nation’s “obesity epidemic” in 2001 and new studies suggesting fat restriction was hardly a magic bullet for public health, doubts crept in about our diets—raising a muddle of competing explanations about what had happened and what we should do.

Had we simply “gone too far” with the low-fat emphasis, inadvertently placing a halo around carbohydrate-laden snacks and juices? Maybe the low-fat approach had never been based on adequate science? Could it be that the real devil in the American diet was actually sugar—a seductive toxin that had slipped into so many foods? Or what about the age-old idea that people were simply eating too much and moving too little? A storm of discordant advice swept through the nutrition field. Low-carb rebels duked it out in the press with their low-fat elders. Who was right? Who could be trusted? And who was to blame for our nutritional befuddlement?

In late 2016, there emerged an explanation that appeared to cut through the fog: It was the sugar industry. Researchers with the University of California announced they had unearthed secret archival documents showing that in the mid-1960s, the industry-backed Sugar Research Foundation had covertly paid top scientists at Harvard to conduct a literature review playing down the role of sugar in heart disease and pinning the blame on dietary fat instead.Marion Nestle, a renowned nutrition professor and authority on corporate influence, suggested the findings were a “smoking gun.” As many as “five decades of research into the role of nutrition and heart disease, including many of today’s dietary recommendations, may have been largely shaped by the sugar industry,” reported the New York Times. The story was like a chocolate kiss to the media’s sweet tooth for conspiratorial dramas: Big Sugar had cooked up the low-fat diet. Just this week, David Leonhardt, a Times op-ed columnist turned diet guru, assailed Big Sugar for having tricked us with “false” research and unveiled his own guide on “How to Stop Eating Sugar.” Leonhardt underscored that going sugar-free could be seen as “a political act: resisting the sugar industry’s attempts to profit off your body.”

But as we detailed last month in Science, our own examination of the historical events in question shows this alluring tale of industry meddling is based on a highly selective and profoundly flawed interpretation of the history. The long-deceased Mad Men–era Harvard scientists who stand accused of having been “paid off” to “shift the blame” to fat were, in fact, already on record in support of low-fat diets as a way to fight heart disease for nearly a decade before the sugar men came calling. In adopting this stance they were in sync with the dominant nutritional paradigm of the era: the idea that the fatty American diet, by raising cholesterol levels in the blood, was behind the epidemic of heart attacks that was killing so many middle-aged breadwinners. No blame-shifting was even required!

There is a rich tradition in contested areas of science of using bits and pieces of history to add urgency to one’sclaims.

Moreover, the Harvard nutritionists were approached by the sugar industry based on the results of a landmark study they had just completed—and would soon publish in peer-reviewed journals—that appeared to confirm that eating a lot of butter and meat put the heart at risk and that consuming high-sugar diets had little effect. That study had been funded by the U.S. dairy industry, but the results wiped the smiles right off dairymen’s milk-mustached faces. When the sugar industry subsequently commissioned the Harvard men to conduct a literature review, it was simply an attempt to amplify their pre-existing, data-driven conclusions. There was no “smoking gun.” Bernard Lown, a cardiologist who worked in Harvard’s nutrition department during the 1960s (and later shared the 1985 Nobel Peace Prize with a Soviet physician for their advocacy on the prevention of nuclear war), told us that the claim that the sugar industry bought off his former co-workers was simply “an invention after the fact about what happened.”

So what explains the emergence of this shadowy narrative about Big Sugar? Certainly there is a rich tradition in contested areas of science of using bits and pieces of history to add urgency to one’s claims. Over the past 20 years, a wave of popular articles and books written by advocates of low-carbohydrate diets have cast an ensemble of scientific heroes and villains to explain the embattled history of nutrition. On the villainous side, there are the low-fat zealots, whose purported hubris and possible sympathies with the sugar industry led them to place too much faith in their own data. On the hero side, there are the handful of noble, independent scientists who courageously challenged the dietary fat paradigm and zeroed in on sugar instead. The major beneficiary of this nutritional lionization has been John Yudkin, a prominent British nutritionist who declared sugar to be Pure, White and Deadly in 1972 in a widely read popular book.

Among the most enthusiastic of the Yudkin revivalists has been Robert Lustig, a pediatric endocrinologist who believes sugar is a toxin and whose powerful 2009 lecture “Sugar: The Bitter Truth” has become a viral sensation on YouTube. Lustig penned an introduction to the 2012 reissue of Yudkin’s sugar book (it had gone out of print), in which he refers to himself as a “Yudkin disciple” and Yudkin’s writings as “prophecy.” He laments Yudkin’s ill-fated struggles with the high priests of nutrition who bought into what Lustig calls the “propaganda of ‘low-fat’ ” and blames them for tossing Yudkin and his sugar hypothesis “under the proverbial bus.”

Much of this narrative comes from Yudkin himself. In addition to articulating his case against sugar, Pure, White and Deadly tells a tale of what it’s like to be a researcher “who makes discoveries and holds opinions that a lot of people don’t like”—an “objective scientist” under attack by researchers committed to the low-fat paradigm and operatives of the sugar industry. This ballad of John Yudkin as tragic visionary has received wide press play in recent years, with one 2016 Guardian article arguing that the pattern of industry meddling and “unscientific” disregard for Yudkin’s ideas had amounted to a “sugar conspiracy.” “Yudkin correctly fingered the sugar and food industries for what they were, and still are,” wrote Lustig in his introduction to Yudkin’s book. “Those who don’t understand history are condemned to repeat it—especially in the face of persistent propaganda. And this book is history.”

And yet Yudkin’s book is not a work of history or a scientific document: It is a professional memoir and popular book on diet and nutrition. And while it is true, as Yudkin divulges, that his sugar theory aroused opposition from those who believed saturated fat was the culprit in heart disease, the image of him as a shunned prophet, preaching in the wilderness and hounded by agents of industry, leaves out the extent to which his research was disbelieved mainly because the evidence supporting it did not hold up to scrutiny. High-profile attempts to replicate Yudkin’s signature finding that heart attack sufferers tended to be heavy sugar users flat-out failed.

Present-day Yudkin disciples have also looked past the extent to which his research was richly supported by the food industry. In the late 1960s, the International Dairy Federation paid Yudkin to conduct sugar studies in pigs, rats, cockerels, and humans. He regularly took the stage at National Dairy Council press events in Europe and the U.S., promoting his sugar theory and the benefits of milk and butter. Stumping for butter during that period was like defending Coca-Cola today. Yudkin acknowledged in interviews that Big Butter gave him money “to distract attention from the dangers of their own products” yet insisted it was “a slur on the integrity of many nutritionists to imply that those who advise food manufacturers are inevitably tainted.”

Today Yudkin’s industry-friendly attitude looks naïve, or even a bit shady: Our subsequent experiences with deceit and denial at the hands of the tobacco industry and other “merchants of doubt” has shown how devious industries can be in using financial incentives to subtly shape the science. Yet in Yudkin’s heyday, industry-academy collaborations carried much less stigma—a vast cultural shift that present-day chroniclers of the purported misdeeds of industry-linked Harvard scientists have overlooked. When Yudkin told an audience of poultry producers in 1973 that “when you are deciding on your last course at the restaurant, remember—Cheese soufflé? YES! Chocolate soufflé? NO!” he was speaking as a researcher who would soon embark on a yolk-positive public relations tour that one reporter called “a counter offensive for the egg,” but he did not believe his scientific ideas were any less sound because of it.

But conspiratorial tales, when not grounded in strong evidence, can pose a real danger to our ability to make good public health policies and understand how science actuallyworks.

Narratives about industry meddling in scientific research can provide seductive explanations for twists and turns in science and policy. The claim that Big Sugar helped cook up the low-fat diet has appealed to different constituencies for different reasons: scientists who think sucrose is an addictive toxin, public health watchdogs wary of Big Tobacco–style interference in nutrition, journalists drawn to juicy stories about corruption, nutritionists who once argued fat was the central dietary danger and have since felt the ground wobble beneath their feet.

But conspiratorial tales, when not grounded in strong evidence, can pose a real danger to our ability to make good public health policies and understand how science actually works. Stories about clandestine payoffs and corporate cover-ups by definition suggest that some scandalous truth was being hidden (e.g., sugar is the real devil, not fat!). The act of uncovering apparent greedy meddling can provide a powerful stimulant to action (e.g., the sugar industry tricked us—we won’t get fooled again!). Normal developments and detours in science and policy are recast as the product of dark industrial forces. The only lesson to be learned is to keep science at arm’s length from the profiteering of corporations. As we pinwheel from lipophobia to sucrophobia, any reckoning with the zigzags of nutrition science may seem like a distraction.

Avoiding these traps requires a commitment to evidence and an appreciation for the complexity of scientific research and its history. While we support efforts to impose taxes on soda and other sugar-sweetened beverages, we believe that the real enemies in modern nutrition are hyperbole and oversimplification. The fight against obesity need not rely on artificially sweetened renderings of the past.